Jung Mi Oh

Pharmacokinetics of drugs in rats with diabetes mellitus induced by alloxan or streptozocin: comparison with those in patients with type I diabetes mellitus

Objectives In rats with diabetes mellitus induced by alloxan (DMIA) or streptozocin (DMIS), changes in the cytochrome P450 (CYP) isozymes in the liver, lung, kidney, intestine, brain, and testis have been reported based on Western blot analysis, Northern blot analysis, and various enzyme activities. Changes in phase II enzyme activities have been reported also. Hence, in this review, changes in the pharmacokinetics of drugs that were mainly conjugated and metabolized via CYPs or phase II isozymes in rats with DMIA or DMIS, as reported in various literature, have been explained. The changes in the pharmacokinetics of drugs that were mainly conjugated and mainly metabolized in the kidney, and that were excreted mainly via the kidney or bile in DMIA or DMIS rats were reviewed also. For drugs mainly metabolized via hepatic CYP isozymes, the changes in the total area under the plasma concentration–time curve from time zero to time infinity (AUC) of metabolites, AUCmetabolite/AUCparent drug ratios, or the time‐averaged nonrenal and total body clearances (CLNR and CL, respectively) of parent drugs as reported in the literature have been compared.

Epigenetic changes in gene expression for drug-metabolizing enzymes and transporters.

Individual differences in drug response can be caused by genetic and epigenetic variability and disease determinants. Pharmacoepigenetics is a new field that studies the expression changes in pharmacogenes without changes in DNA sequences. Epigenetic control mechanisms are associated with DNA methylation, histone modification, small noncoding RNAs, and nucleosome remodeling. Researchers are actively attempting to identify epigenetic mechanisms for controlling the expression of enzymes and transporters affecting the metabolism and disposition of drugs. Current evidence suggests that epigenetic changes play a major role in cytochrome P450 enzyme expression, major transporter function, and in interactions with nuclear receptors. A thorough understanding of pharmacoepigenetics provides insight into new approaches to drug discovery and development, provides an understanding of previously observed actions of older drugs, and provides a pathway by which epigenetics can be harnessed to provide better patient‐specific therapy.

Combinational effect of intestinal and hepatic CYP3A5 genotypes on tacrolimus pharmacokinetics in recipients of living donor liver transplantation.

Background For living donor liver transplantation, the genetic association of CYP3A5 genotype of recipient’s native intestine and donor’s liver allograft with tacrolimus pharmacokinetics has not been explained completely considering liver regeneration time. The goal of the study was to investigate the longitudinal effects of recipient-donor combinational CYP3A5 genotypes on tacrolimus dose-normalized concentration (C/D ratio) in blood. Methods Tacrolimus blood concentrations were measured for 58 Korean adult living donor liver transplant recipients on tacrolimus-based immunosuppressants during 4 years of follow-up. CYP3A5 was genotyped for both recipient and donor, and the recipient-donor combinational genetic effect on tacrolimus C/D ratios were evaluated as a function of time after adjusting for covariates including demographics and clinical variables. Results CYP3A5 expresser recipients grafted from CYP3A5 expresser donors consistently had the least C/D ratio throughout the entire study period, whereas CYP3A5 expresser recipients grafted from CYP3A5 nonexpresser donors had an intermediate, and CYP3A5 nonexpresser recipients grafted from CYP3A5 nonexpresser donors had the largest C/D ratio (all P < 0.01). The CYP3A5 nonexpresser recipients grafted from CYP3A5 expresser donors showed a significant decrease from the largest to the intermediate in C/D ratio for the first month. Conclusions CYP3A5 genotypes of both recipient and donor were important factors influencing pharmacokinetic variability of tacrolimus. The recipient-donor combinational genetic effect on C/D ratio changed over time after transplantation.

Protective Effects of Haematococcus Astaxanthin on Oxidative Stress in Healthy Smokers

Free radicals induced by cigarette smoking have been strongly linked to increased oxidative stress in vivo, contributing to the pathobiology of various diseases. This study was performed to investigate the effects of Haematococcus astaxanthin (ASX), which has been known to be a potent antioxidant, on oxidative stress in smokers. Thirty-nine heavy smokers (≥20 cigarettes/day) and 39 non-smokers were enrolled in this study. Smokers were randomly divided into three dosage groups to receive ASX at doses of 5, 20, or 40 mg (n=13, each) once daily for 3 weeks. Oxidative stress biomarkers such as malondialdehyde, isoprostane, superoxide dismutase, and total antioxidant capacity, and ASX levels in plasma were measured at baseline and after 1, 2, and 3 weeks of treatment. Compared with baseline, the plasma malondialdehyde and isoprostane levels decreased, whereas superoxide dismutase level and total antioxidant capacity increased in all ASX intervention groups over the 3-week period. In particular, isoprostane levels showed a significant dose-dependent decrease after ASX intake. The results suggest that ASX supplementation might prevent oxidative damage in smokers by suppressing lipid peroxidation and stimulating the activity of the antioxidant system in smokers.

Comparison of lenograstim and filgrastim on haematological effects after autologous peripheral blood stem cell transplantation with high-dose chemotherapy

SUMMARY Objective: To compare the efficacy of lenograstim and filgrastim on haematological recovery following an autologous peripheral blood stem cell transplantation (PBSCT) with high-dose chemotherapy. Methods: A retrospective case-controlled study. Results: Absolute neutrophil count (ANC) recovery above 0.5 × 109 l−1 and white blood cell (WBC) recovery above 4 × 109 l−1 for 3 consecutive days was achieved earlier with filgrastim than with lenograstim ((13.2 ± 8.0 vs 19.0 ± 10.0 days, p = 0.004), (16.9 ± 9.7 vs 29.9 ± 16.6 days, p = 0.001), respectively). The platelet recovery above 20 x 109/l was also achieved earlier with filgrastim than with lenograstim (19.5 ± 11.6 vs 27.2 ± 13.8 days, p = 0.006). Furthermore, filgrastim-treated patients received fewer days of granulocyte colony simulating factor (G-CSF) administration (12.5 ± 7.0 vs 18.6 ± 8.5 days, p = 0.001) and spent less time in hospital (23.7 ± 10.9 vs 32.0 ± 17.6 days, p = 0.009). Duration of antibiotic administration was also significantly shorter in the filgrastim group (13.6 ± 7.6 vs 29.1 ± 19.8 days, p = 0.001). Conclusion: In patients undergoing PBSCT following high-dose chemotherapy, filgrastim significantly reduced the duration of neutropenia, thrombocytopenia and days of G-CSF administration, and led to earlier hospital discharge compared with lenograstim.

Gene–gene interaction analysis for the survival phenotype based on the Cox model

Motivation: For the past few decades, many statistical methods in genome-wide association studies (GWAS) have been developed to identify SNP–SNP interactions for case-control studies. However, there has been less work for prospective cohort studies, involving the survival time. Recently, Gui et al. (2011) proposed a novel method, called Surv-MDR, for detecting gene–gene interactions associated with survival time. Surv-MDR is an extension of the multifactor dimensionality reduction (MDR) method to the survival phenotype by using the log-rank test for defining a binary attribute. However, the Surv-MDR method has some drawbacks in the sense that it needs more intensive computations and does not allow for a covariate adjustment. In this article, we propose a new approach, called Cox-MDR, which is an extension of the generalized multifactor dimensionality reduction (GMDR) to the survival phenotype by using a martingale residual as a score to classify multi-level genotypes as high- and low-risk groups. The advantages of Cox-MDR over Surv-MDR are to allow for the effects of discrete and quantitative covariates in the frame of Cox regression model and to require less computation than Surv-MDR. Results: Through simulation studies, we compared the power of Cox-MDR with those of Surv-MDR and Cox regression model for various heritability and minor allele frequency combinations without and with adjusting for covariate. We found that Cox-MDR and Cox regression model perform better than Surv-MDR for low minor allele frequency of 0.2, but Surv-MDR has high power for minor allele frequency of 0.4. However, when the effect of covariate is adjusted for, Cox-MDR and Cox regression model perform much better than Surv-MDR. We also compared the performance of Cox-MDR and Surv-MDR for a real data of leukemia patients to detect the gene–gene interactions with the survival time. Contact: leesy@sejong.ac.kr; tspark@snu.ac.kr

Combined interaction of multi-locus genetic polymorphisms in cytarabine arabinoside metabolic pathway on clinical outcomes in adult acute myeloid leukaemia (AML) patients

Cytarabine arabinoside (ara-C) is the key agent for treating acute myeloid leukaemia (AML). Here, we genotyped 139 single nucleotide polymorphisms (SNPs) within the ara-C transport and metabolic pathway using the Illumina Golden Gate Assay in 97 patients with previously non-treated de novo AML other than M3. DCK rs4694362 (CC genotype) was a significant poor prognostic factor for overall survival (OS) (hazard ratio [HR], 33.202 [95% confidence interval (CI), 4.937-223.273], P<0.0001, P(Bonferroni)=0.017). SLC29A1 rs3734703 (AA or AC genotype) in combination with TYMS rs2612100 (AA genotype) was significantly associated with shorter relapse free survival (RFS) (HR, 17.630 [95% CI, 4.829-64.369], P<0.0001, P(Bonferroni)=0.021). These SNPs showed moderate or large inter ethnic divergence in allele frequencies from African or Caucasian populations. The results of our study suggest that a single SNP and SNP-SNP interactions may help to predict the drug response and provide a guide in developing individualised chemotherapy for AML patients receiving ara-C based chemotherapy.

Factors affecting the apparent clearance of tacrolimus in Korean adult liver transplant recipients.

Study Objective. To identify the factors affecting tacrolimus apparent total body clearance (Cl/F [F = bioavailability]) in adult liver transplant recipients.

ABCB1 C3435T Genetic Polymorphism on Population Pharmacokinetics of Methotrexate After Hematopoietic Stem Cell Transplantation in Korean Patients: A Prospective Analysis

BACKGROUND Methotrexate (MTX) is often used to prevent graft-versus-host disease (GVHD) after allogeneic hematopoietic stem cell transplantation (HSCT). However, MTX has great pharmacokinetic variability and its use can result in fatal complications and/or infections after HSCT. OBJECTIVES The purposes of this study were to build a population pharmacokinetic model of MTX treatment in Korean patients who have undergone HSCT and to identify covariates, including genetic polymorphisms, that affect the pharmacokinetic properties of MTX. METHODS Clinical characteristics and MTX concentration data for 20 post-HSCT patients were collected. For each patient, ABCB1, ABCC2, ATIC, GGH, MTHFR, and TYMS genotyping was performed. Population pharmacokinetic analysis was performed using the NONMEM program. Analysis of MTX pharmacokinetic properties was accomplished using a 2-compartment pharmacokinetic model that incorporated first-order conditional estimation methods with interaction. The effects of a variety of demographic and genetic factors on MTX disposition were investigated. RESULTS The study population consisted of 12 men (60%) and 8 women (40%). Median age and body weight were 28 years (range, 18-49 years) and 55.6 kg (range, 44.8-80.8 kg), respectively. Within the study population, the estimated mean MTX clearance (CL) was 7.08 L/h, whereas the mean central compartment volume (V(1)) of MTX distribution was 19.4 L. MTX CL was significantly affected by glomerular filtration rate (GFR), penicillin use, and the ABCB1 3435 genotype. Interindividual variabilities for CL and V(1) were 21.6% and 73.3%. A 10-mL/min GFR increase was associated with a 32% increase in mean MTX CL, whereas penicillin use was associated with a decrease in MTX CL of 61%. MTX CL was significantly greater (by ∼21%) in patients with the ABCB1 3435 CC and CT genotype than in those with the ABCB1 3435 TT genotype (P < 0.001). CONCLUSIONS There was great interindividual variation in MTX pharmacokinetic properties in patients who had undergone HSCT. GFR, concurrent penicillin use, and the presence of the ABCB1 3435 C

Population pharmacokinetic-pharmacogenetic model of tacrolimus in the early period after kidney transplantation.

As tacrolimus has a rather narrow therapeutic range and high individual variability in its pharmacokinetics, it is important to determine the cause of the variation in tacrolimus pharmacokinetics. The purpose of this study was to establish a population pharmacokinetic–pharmacogenetic model of tacrolimus and identify covariates that affect pharmacokinetic parameters to prevent fluctuations in the tacrolimus trough concentration during the early period after transplantation. Data from 1501 trough concentrations and 417 densely collected concentrations were compiled from 122 patients who were on post‐operative days 10–20 and analysed with a nonlinear mixed‐effect model. The first‐order conditional estimation (FOCE) with interaction method was used to fit the model using the NONMEM program. Clinical/laboratory data were also collected for the same period, and CYP3A5 and ABCB1 genotypes were analysed for use in modelling from all included patients. An empirical Bayesian approach was used to estimate individual pharmacokinetic profiles. A one‐compartment model with first absorption and elimination and lag time best described the data. The estimated population mean of clearance (CL/F), volume of distribution (V/F) and absorption rate (Ka) were 21.9 L/hr, 205 L, and 3.43/hr, respectively, and the lag time was fixed at 0.25 hr. Clearance increased with days after transplantation and decreased with CYP3A5*3/*3 about 18.4% compared with CYP3A5*1 carriers (p < 0.001). A population pharmacokinetic model was developed for tacrolimus in early post‐kidney transplantation recipients to identify covariates that affect tacrolimus pharmacokinetics. Post‐operative days and CYP3A5 genotype were confirmed as critical factors of tacrolimus pharmacokinetics.